The following Participating Institutions are custodians for this species in the CPC National Collection:
Mercer Arboretum and Botanic Gardens
The conservation of Hymenoxys texana is fully sponsored.
Dave Berkshire contributed to this Plant Profile.
Prairie dawn is a member of the sunflower family, but this small annual only reaches a height of seven inches and so is often overlooked. This plant is found only in the open grasslands of the northern part of the Gulf Prairie region of Harris and Fort Bend Counties of Texas. In late winter its oblong, somewhat fleshy leaves cluster at the plant base and in late February to April a small (0.15-0.23 inch long) round head of yellow disk flowers appears. The minute ray flowers are concealed by the bracts. The plant sets seeds from April to May and dies before the bare ground dries and cracks in the summer heat. The seeds are cone-shaped and hairy. (Stark 1996).
Prairie Dawn was first collected near Hockley in Harris County, Texas in 1889. Thought to be extinct (Correll and Johnston 1979), the plant was rediscovered north of Cypress in Harris County in 1981 by James Kessler (Mahler 1982 & 1983).
Distribution & Occurrence
Grows within a narrow range of soil and site conditions in the open grasslands of the northern part of the Gulf Prairie region. Slick areas composed of fine-sandy compacted soil occur in seasonally wet depressions or saline swales at the periphery of low mounds termed mima or pimple mounds (Stark 1996). The upper 7 inches of the soils, in the Narta soil series, are poorly drained and are powdery when dry and sticky and soft when wet. These soils are often saline and moderately alkaline. Little water is available to plant roots beyond the upper 7 inches. Plants endure soil conditions ranging from saturated during the winter to droughty in the summer. Hymenoxys texana also persists in the low areas of abandoned rice fields, vacant lots, and pastures where mima mounds have been bulldozed and natural vegetation has returned. Prairie Dawn does not colonize recently disturbed soils and is susceptible to competition.
Plants that grow in association with Prairie Dawn include Short-spike Windmillgrass, the rare Texas Windmillgrass, Gulf Cordgrass, Whorled Dropseed, Filly Panicum, Little Barley, Annual Bentgrass, Bearded Flatsedge, False Onion, Bottlebrush Plantain, Pepperweed, Sandparsley, the rare Houston Camphor Daisy, Western Dwarf-dandelion, Chaffweed, Golden Hedgehyssop, Common evax, Prairie Flameflower, Purslane, Wine-cup, Cotton-flower, Silky Evolvulus and Bracted Sida (Stark 1996).
|Since 1986, populations found in Harris and Fort Bend Counties may total ~ 50 sites comprising an unknown number of individuals (Stark 1996).|
Conservation, Ecology & Research
heavy grazing by cattle and primarily,
urban development (road construction and residential development) of the Coastal Prairies, especially within the Houston city limits where these plants are found.
Germination and growth to maturity studies at Mercer Arboretum and Botanic Gardens in 1988-89 revealed non-specific soil requirements and ease of cultivation. Seedlings, however, do not tolerate extended periods of submerging.
Public educational display plants for the Endangered Species Garden at Mercer are germinated within our greenhouses. The Endangered Species Garden established in 1994 with support from Star Enterprises displays rare native plants for the public to view year-round. In Spring 2002, the River Oaks Garden Club of Houston, TX provided a generous gift to begin the expansion and renovation of Mercers Endangered Species Garden. Plants produced for educational display gardens or for specific restoration and reintroduction projects are produced within Mercers nursery greenhouses and within our Conservation Area. The Conservation Area provides secure, raised beds for mass propagation of plants/seeds. Each bed is provided with independently controlled irrigation and substrates that meet the unique requirements for each species.
Seeds from several sites within Harris County collected by Dr. Larry Brown of Houston Community College and Ralph Taylor of the Harris County Flood Control District are stored at Mercer Arboretum and Botanic Gardens. Banked wild-collected seed date to 1988. Mercer also banks subsets of rare seeds collected from field surveys and from propagation work with our collaborating CPC institution, the Lady Bird Johnson Wildflower Center, Austin, TX and the National Center for Genetic Resources Preservation (NCGRP) in Ft. Collins, CO (formerly called the National Seed Storage Laboratories.
Seeds from an in-house propagation of 1993 that had been in storage in Mercer's seed bank freezer germinated under greenhouse conditions at ~70% with ~50% survivorship during the Winter of 2001. Plants germinated in our greenhouses are used for display in our Endangered Species Garden and Mercer's Plaza and displays for off-site conservation programs given by Mercer.
http://www.cp4.hctx.net/mercer/mplant.htm. This article appeared in Harris County Precinct 4 magazine, Parkscape, Autumn 2001 and reached 33,000 possible readers. Harris County Precinct 4 magazine, Parkscape publishes public information articles about the plant conservation efforts of Mercer Arboretum and Botanic Gardens. 115,000 issues are circulated annually of this quarterly publication. Articles about rare plants maintained at Mercer may be viewed at: http://www.cp4.hctx.net/mercer/mplant.htm.
Propagation of seed for reintroduction efforts.
Correll, D.S.; Johnston, M.C. 1970. Manual of the vascular plants of Texas, 1676-80. Texas Research Foundation.
Lowe, D.W.; Matthews, J.R.; Moseley, C.J. 1990. The official World Wildlife Fund guide to endangered species of North America. Vol. 1. Washington, D.C. Beacham Publishing.
Poole, J.M.; Carr, W.R.; Price, D.M.; Singhurst, J.R. 2007. Rare Plants of Texas. College Station, TX. Texas A&M University Press. 640p.
Tveten, J.L.; Tveten, G.A. 1993. Wildflowers of Houston. Houston, Texas: Rice University Press. 309p.